[REVISION HISTORY]

New World screwworm re-emergence in the United States

Updated 3 times since CLSTR started tracking revisions of this situation.

What changed

2026-09-08 01:43 UTC → 2026-09-08 07:20 UTC · added ~~removed~~

The New World screwworm, a parasitic fly known as Cochliomyia hominivorax, has re-emerged in the United States after being eradicated in 1966. The parasite, which burrows into and consumes the living tissue of warm-blooded animals, has spread northward through Central America and Mexico toward U.S. borders, driven by warming climates and livestock movement. In response to the threat to livestock and wildlife in regions such as Texas and New Mexico, USDA researchers have developed NovoFly™, an all-male strain designed to enhance the efficiency of the Sterile Insect Technique (SIT). With regulatory approval, researchers can now focus on producing only male flies, a shift expected to double the number of flies available for SIT releases to eradicate populations or isolate new outbreaks. The USDA is now deploying NovoFly™ as part of a massive coordinated response involving the United States, Mexico, and Panama. This biological control effort follows a 2023 breach of containment lines in the Darien Gap, which led to infestations in Panama and Mexico, as well as confirmed cases in the U.S. Facilities in Chiapas, Mexico, and Panama are supporting fly releases to prevent economic damages estimated at $2.5 billion in the Southwest United States alone. As of September 2026, the United States has reached a milestone of releasing one billion sterile ~~flies.~~ flies, with the billionth fly released in Texas. While the USDA has confirmed 48 cases in the U.S. since June, production capacity is struggling to meet demand. U.S. Agriculture Secretary Brooke Rollins stated that the country requires “400-500 million flies per week,” but existing facilities in Panama and Mexico currently produce only approximately 100 million flies per week each. In Mexico, authorities have released 73.9 million sterile flies across strategic sites in Chihuahua and Sonora. These efforts have already shown results in Chihuahua, where active cases decreased by 71%, falling from 227 to 64. To support these biological controls, Senasica has inspected thousands of livestock production units and treated over 100,000 animals with preventive medications.

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